POLARIMETRIC SCANNING RADIOMETER C AND X-BAND MICROWAVE OBSERVATIONS DURING SMEX03.

Authors: Jackson, Thomas; BINDLISH, R - SSAI; GASIEWSKI, A - NOAA; STANKOV, B - NOAA; KLEIN, M - NOAA; NJOKU, E - NASA JPL; Bosch, David - Dave; COLEMAN, T - ALABAMA A&M UNIV.; LAYMON, C - NASA MSFC; Starks, Patrick

Submitted to: IEEE Transactions on Geoscience and Remote Sensing
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2005
Publication Date: 11/1/2005
Citation: Jackson, T.J., Bindlish, R., Gasiewski, A.J., Stankov, B., Klein, M., Njoku, E.G., Bosch, D., Coleman, T.L., Laymon, C., Starks, P. 2005. Polarimetric Scanning Radiometer C and X band microwave observations during SMEX03. IEEE Transactions on Geoscience and Remote Sensing. 43:2418-2430.

Interpretive Summary: The scaling of microwave brightness temperature from aircraft to satellite spatial resolutions was established through a large-scale field experiment. Microwave brightness temperature results obtained using an aircraft based simulator of an operating satellite instrument were analyzed as part of Soil Moisture Experiments 2003 (SMEX03) conducted in four diverse regions were utilized. The value of the data collected in Oklahoma for this portion of the analysis was very limited to a small range of observed moisture conditions. Data collected in Alabama included a wide range of antecedent rainfall conditions and diverse vegetation cover. Results indicated a lack of sensitivity to rainfall/soil moisture under the forest canopy conditions typical of the region at C-bands. Validation of the soil moisture products, as well as the brightness temperatures over land, from satellite instruments is a critical issue and one that is difficult to address. The coarse spatial scale of these passive microwave instruments (40 to 75 km)and the high temporal and spatial variability of the soil moisture fields make extensive sampling and replication difficult and costly. The results of the analyses conducted here have established the quality of both the aircraft and satellite data collected in SMEX03. With this knowledge, further soil moisture and geophysical interpretations can be performed with confidence.

Technical Abstract: Soil Moisture Experiment 2003 (SEMX03) was the second in a series of field campaigns using the National Oceanic and Atmospheric Administration (NOAA) Polarimetric Scanning Radiometer (PSR/CX) designed to validate brightness temperature data and soil moisture retrieval algorithms for the Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) on the Aqua satellite. Objectives related to the PSR/CX during SMEX03 included: calibration and validation of AMSR-E brightness temperature observations over different climate/vegetation regions of the U.S. (Alabama, Georgia, Oklahoma), identification of possible areas of Radio Frequency Interference (RFI), comparison of X-band observations from Tropical Rainfall Measurement Mission )TRMM)-Microwave Imager (TMI), AMSR-E and PSR?cx, and exploring the potential of soil moisture retrieval algorithms using C and X-band imagery in diverse landscapes. In the current investigation, more than one hundred flightlines of PSR/CX data were extensively processed to produce gridded brightness temperature products for the four study regions. Due to the lack of significant rainfall in Oklahoma, generally dry soil moisture conditions were observed. Observations obtained over Alabama include a wide range of soil moisture and vegetation conditions. Results from the Alabama site clearly showed a lack of sensitivity to rainfall/soil moisture under forest canopy cover. Quantitative comparisons made with the TMI validated that both the PSR/CX and AMSR-E X-band channels were well calibrated. Spectral analyses indicated that the PSR/CX observations at C-band also are reasonable. As expected, there were varying degrees of radio frequency interference in the AMSR-E C-band data for the study sites that will prevent further soil moisture analysis using these data. X-band comparisons of the PSR/CX high resolution and AMSR-E and TMI low-resolution data indicated a linear scaling for the range of conditions studied in SMEX03. These results will form the basis for further soil moisture investigations.